Preparation:

Mix cranberries, onions, and 1 cup water in a large (at least 1 gallon) enamel or stainless-steel kettle, cover, and simmer 20 to 30 minutes, stirring now and then, until mushy.

Puree, a little at a time, by buzzing 20 to 30 seconds in an electric blender at low speed or 15 to 20 seconds in a food processor fitted with the metal chopping blade, or put through a food mill. Press through a fine sieve.

Place in a clean large kettle and cook, uncovered, at a slow boil until volume is reduced by half. (Note: It is important that kettle be large to keep ketchup from spattering all over your kitchen.)

Meanwhile, wash and sterilize 2 (1-pint) jars and their closures, stand them on a baking sheet, and keep warm in a 250-degree F. oven until needed.

Tie celery seeds, mustard seeds, allspice, cinnamon, peppercorns, and bay leaves in cheesecloth and add to kettle along with salt, set lid on askew, and simmer 1/2 hour. Remove spice bag, add vinegar and sugar, and cook, uncovered, at a slow boil, stirring frequently, until very thick. (Note: Toward the end, you will have to stir constantly to prevent scorching.)